This invention relates to amorphous aluminosilicates stable at high temperature and more particularly relates to amorphous silica-rich aluminosilicates useful as coatings suitable for use at high to extreme temperatures.
High performance, high temperature resistant materials are needed for applications that experience high to extreme temperature conditions normally in excess of 1000 or 1200° C. or above. Interest in Ultra-High Temperature Ceramic (UHTC) materials is rapidly emerging with diverse needs for protective coatings for temperatures ranging above 1500° C. In such environments, material degradation from corrosion, which may be accelerated by air, moisture, salt, or other contaminants, poses a serious problem in advanced materials used and being designed for air and space vehicles and other high performance applications. Ceramic refractory materials are used in extreme environments such as in glass making, metal production, and others uses which are prone to degradation from sintering (porosity goes down and so does the toughness) or environmental attack. In both cases, if a coating acts as a good barrier against sintering or gases that diffuse from external atmospheres, the life of the refractory may be extended significantly and this could save high costs for replacement and/or repair. High temperature resistant coatings also would be useful in protecting an article made from a suitable substrate such as a ceramic used in such applications. In addition, such materials may have engineered porosity (open and/or closed), which is useful in maintaining targeted performance in end-use applications. Typically, residual porosity in a bulk material is tailored for imparting lower weight while maintaining or improving toughness of an article. A beneficial coating system would not significantly decrease or degrade the engineered porosity (and thereby degrade performance characteristics based on such porosity) while protecting a substrate from corrosion/oxidation or other degradation under high temperature conditions such as in excess of 1500° C.